Rapid preparation of tritium-labeled bile acids by enolic exchange on basic alumina containing tritiated water.
When a 3-keto bile acid methyl ester was chromatographed on basic alumina inactivated with tritiated water, the enolic hydrogen atoms at C-2 and C-4 exchanged with tritium atoms. The (3)H-labeled keto ester was reduced with borohydride, and the resultant mixture of 3alpha- and 3-hydroxy epimers was resolved by preparative thin-layer chromatography to yield a pure 2,4-(3)H-labeled bile acid ester. Lithocholic, chenodeoxycholic, deoxycholic, and cholic acids having a specific activity of 1-10 micro c/ micromole were prepared from their 3-keto derivatives. The tritium label remained intact during alkaline saponification in vitro and enterohepatic cycling in vivo in human subjects.
D000535:Aluminum; D001647:Bile Acids and Salts / Q000138:chemical synthesis*; D002247:Carbon Isotopes; D002845:Chromatography; D002855:Chromatography, Thin Layer; D004355:Drug Stability; D004952:Esters; D007651:Keto Acids; D008722:Methods; D010087:Oxides; D013237:Stereoisomerism; D014316:Tritium; D014867:Water
D001647:Bile Acids and Salts; D002247:Carbon Isotopes; D004952:Esters; D007651:Keto Acids; D010087:Oxides; D014867:Water; D014316:Tritium; D000535:Aluminum